Add MCP tools for migration inspection (bd-627d Phase 3)

- Add inspect_migration() tool - calls bd migrate --inspect --json
- Add get_schema_info() tool - calls bd info --schema --json
- Implements abstract methods in BdClientBase
- CLI client calls commands directly
- Daemon client raises NotImplementedError (rare admin commands)

Phase 3 complete. Agents can now inspect migrations via MCP before running them.

Amp-Thread-ID: https://ampcode.com/threads/T-de7e1141-87ac-4b4a-9cea-1b7bc4d51da9
Co-authored-by: Amp <amp@ampcode.com>

integrations/beads-mcp/src/beads_mcp/bd_client.py

@@ -129,6 +129,16 @@ class BdClientBase(ABC):
         """Initialize a new beads database."""
         pass
 
+    @abstractmethod
+    async def inspect_migration(self) -> dict:
+        """Get migration plan and database state for agent analysis."""
+        pass
+
+    @abstractmethod
+    async def get_schema_info(self) -> dict:
+        """Get current database schema for inspection."""
+        pass
+
 
 class BdCliClient(BdClientBase):
     """Client for calling bd CLI commands and parsing JSON output."""
@@ -575,6 +585,28 @@ class BdCliClient(BdClientBase):
 
         return [BlockedIssue.model_validate(issue) for issue in data]
 
+    async def inspect_migration(self) -> dict:
+        """Get migration plan and database state for agent analysis.
+
+        Returns:
+            Migration plan dict with registered_migrations, warnings, etc.
+        """
+        data = await self._run_command("migrate", "--inspect")
+        if not isinstance(data, dict):
+            raise BdCommandError("Invalid response for inspect_migration")
+        return data
+
+    async def get_schema_info(self) -> dict:
+        """Get current database schema for inspection.
+
+        Returns:
+            Schema info dict with tables, version, config, sample IDs, etc.
+        """
+        data = await self._run_command("info", "--schema")
+        if not isinstance(data, dict):
+            raise BdCommandError("Invalid response for get_schema_info")
+        return data
+
     async def init(self, params: InitParams | None = None) -> str:
         """Initialize bd in current directory.